What is Causing the Lump in My Armpit?

Published April 11th, 2022 by Corey Riley
Fact Checked by
Erik Rivera
Medically Reviewed:
Dr. Angel Rivera

Lumps in the armpit can be alarming, but many are not cause for concern. If you've discovered a lump in your armpit, you're likely wondering what's causing it.

Armpit lumps can be caused by a variety of things, from swollen or enlarged lymph nodes to a sign of cancer.

It's important to know the symptoms of an unexplained armpit lump and when to see your doctor.

In this article, we will discuss the causes and symptoms of armpit lumps, as well as how your doctor will diagnose them along with the treatment options available to you.

What are lumps in my armpit?

Lumps in the armpit are a common occurrence and are usually caused by a swollen lymph node or lymph gland although there are a variety of other reasons that could be causing it.

Your body has hundreds of lymph nodes that are a part of the lymphatic system, which is a network of tissues and organs that help rid the body of toxins, waste, and other harmful substances and are located throughout your body, including your armpits.

If you have a lump in your armpit, you may need your doctor to diagnose what is causing it so you can start a treatment plan, if necessary.

What causes armpit lumps?

There are a number of things that can cause armpit lumps, the most common being abnormal tissue growth.

However, tissue growth is not always the cause and there may be a serious medical condition causing it which needs to be diagnosed and treated immediately. Other common causes of lumps in your armpit include:


These are noncancerous growths filled with fluid that can form in any part of your body, including your armpits.


Lipomas are fatty lumps that are also noncancerous and can occur anywhere on your body, including the fatty tissue in your armpits.


There are a number of infections, such as skin infections or even bodywide infections, that can cause swollen lymph nodes, which often appear as lumps in the armpit.

Viral infections, bacterial infections, and fungal infections can all cause lumps in your armpits and some can even drain into your armpit causing a lump.


Fibroadenomas are a common type of noncancerous, fibrous growths that usually occur in women between the ages of 15 and 35 although men can get them too, although it is very rare.

They are made up of breast tissue and can often be found in the armpits or as a breast lump.


There are a number of different types of cancer that can cause lumps in your armpits. Lumps in your armpits may be a sign of breast cancer, lymphoma, or leukemia.

While these are all serious conditions, it is important to remember that not all lumps contain cancerous tumor cells.

Allergic reactions

If you have recently started using a new deodorant, antiperspirant, soap, detergent, fabric softener, or any other product that may touch your skin and have developed a lump in your armpit, it is possible that you are allergic to the product.

Allergic reactions due to something touching your skin are called allergic contact dermatitis or irritant contact dermatitis. These allergic reactions can cause irritated skin and swelling which can lead to lumps.


Some vaccinations, such as the MMR (mumps, measles, rubella) vaccine can cause adverse reactions which form lumps in your armpits. These lumps are usually harmless and will go away on their own within a few weeks.


Lupus is an autoimmune disease that can cause a number of different symptoms, one of which is lumps in the armpits. The lumps caused by lupus are usually painless but can be uncomfortable.

What are the symptoms of an armpit lump?

The most common symptom of a suspicious lump in your armpit is obviously a lump that can range in size from small to large.

The lump may also be soft or hard but the texture is dependent on the cause. A painful lump can also occur, but that is not always the case.

However, there are a number of other symptoms that can accompany a lump in your armpit, depending on the underlying cause. These symptoms include:

  • Pain
  • Swelling of your lymph nodes in your armpit and possibly throughout your body
  • Fever
  • Night sweats
  • Reddened skin
  • Normal or hot temperature when touched

Is there a difference in armpit lumps in men and women?

Both women and men can get lumps in their armpits; however, there are some lump types that are more common in women.

For example, fibroadenomas and breast cancer are much more common in women than men. Due to this, if you are a woman and find a lump in your armpit you need to consult with your doctor immediately.

If you are a man, this is not necessary unless the lump is painful or accompanied by other symptoms.

When do I need to see my doctor about an armpit lump?

If you find a lump in your armpit that is small and goes away on its own, it is likely that you do not have to seek medical advice.

If the lump is moderately sized to large, red, painful, and continues to grow larger then you need to seek medical attention. If you are uncertain, please talk to your doctor or healthcare provider.

How does my doctor diagnose an armpit lump?

There are a number of ways that your doctor can diagnose an armpit lump. The first is by doing a physical examination where your doctor will look at the lump and feel for any abnormalities.

Your doctor may also order a blood test or biopsy to rule out infections or to test to see if the lump contains cancer cells. Allergy testing may also be necessary if your doctor suspects an allergic reaction.

Finally, a chest X-ray or mammogram may be ordered for more detailed images if your doctor suspects that the lump is caused by an infection or cancer.

What are the treatment options for an armpit lump?

The treatment options for an armpit lump depend on the underlying cause although some will go away on their own and not require any treatment.

For example, if you have a viral infection, the lump will likely go away on its own within a few weeks or you may need to take topical or oral antibiotics.

If you have a cancerous lump, there are a number of treatment options available including surgery, radiation therapy, and chemotherapy and treatment may vary depending on the type of cancer. Lupus is a chronic condition that cannot be cured but can be managed with medication and other treatments. Cysts or fibrous tissue may need to be surgically removed, although that is not always necessary.

Finally, if you have an allergic reaction, you will need to avoid the allergen that is causing the lump, and over-the-counter (OTC) creams or medications may be used to help lessen the symptoms.


Armpit lumps can be caused by a number of different things including infections, cancer, autoimmune diseases, and allergies.

The lump may be small or large, hard or soft, painless or painful and there are cancerous and benign lumps. If you find a lump in your armpit that is causing you concern, please consult with your doctor or healthcare provider.

They will be able to help you determine the cause and the best course of treatment. If you have any more questions or are uncertain about an armpit lump, please talk to your doctor or health care provider.

References and Sources:

Mayo Clinic